The present invention relates to a load cell weighing apparatus. More particularly, it relates to a weighing apparatus having adjustable load arrestors that can protect various capacity load cells against excessive loads.
Load cells are commonly used in scales because they offer many advantages in comparison to spring and balance scales. For instance, they provide an electrical output which is readily adaptable to the electronics of computing scales. Typically, an electrical detection of the deformation of the load cell is used to determine the weight of the load placed on the scale. Load cells, however, have a disadvantage in that they are easily damaged by overloads and shockloads. Thus, it is necessary to provide overload and shockload protection for load cells in the form of stops, or load arrestors, which limit the deflection of the load cell under a load.
Since different capacity load cells tend to vary slightly in stiffness, it is generally necessary to provide means for the overload protection stops provided in a scale. Further, since full scale deflection is on the order of thousandths of an inch, such adjustments are delicate and particularly difficult to make. In the prior art, the deflection distance is adjusted by adjusting a bolt threaded into the base beneath the load cell. The bolt is then secured with a lock nut to act as a down stop. This approach, however, has several problems. One problem is that securing the lock nut often disturbs the adjustment so that precision is lost. In addition, prior art screw stops require that the pieces be machined, which adds to the total cost of the scale. Thus, the prior art is lacking a simple, yet precise, adjustable load arrestor which is economical to manufacture and comprises a minimum of parts.